Computer-aided design problems of digital microfluidic biochips are receiving much attention, and most of the previous works focus on direct-addressing biochips. In this paper, we solve the placement and droplet routing problem in cross-referencing biochips. In these biochips, the electrodes are addressed in a row-column manner, which may cause electrode interference that prevents simultaneous movements of multiple droplets. We propose a routing algorithm that solves the droplet routing problem directly. A two-coloring graph-theoretic method is used in our router to detect and prevent the electrode interference. In addition, we propose an integer linear programming based method to solve the placement problem. Our method considers the characteristics of cross-referencing biochips and is aware of droplet routing. Real-life benchmarks are used to evaluate the proposed methods. Compared with previous works, our router improves on average 4% in routing time and 58% in runtime. It can route all the benchmarks within the time limits, while the latest work fails in some cases. Moreover, experimental results show that by running our router on the placement result generated by our method and those generated by the latest work, an average improvement of 11%, 29%, 54%, and 46% in the maximum routing time, average routing time, stalling steps, and cell usage can be achieved.